The aim of this study was to determine whether mandibular setback by sagittal split ramus osteotomy (SSRO) influences swallowing function. The subjects were 14 patients with skeletal class III malocclusions who underwent setback surgery by SSRO. Morphological changes were studied on cephalograms, and swallowing function was evaluated by videofluorography before the operation (T0) and at 7-10 days (T1), 3 months (T2), and 6 months (T3) after surgery. The angle between nasion, sella, and hyoid bone (HSN) and the sella-hyoid distance had increased significantly at T1. The hyoid bone returned to the preoperative position at T2. There were no significant changes in the oropharyngeal space at any time. On videofluorographic assessment, lingual movement, soft palate movement, and epiglottic movement had decreased at T1, but all patients recovered at T2. The oral transit time was significantly longer at T1 than at T0. Our results confirm that SSRO influences swallowing function. Swallowing function appears to stabilize by 3 months after surgery.